Developed has been a light modulator element of diffraction grating type which is capable of changing the depth of grating by alternately forming fixed ribbons and moving ribbons on a substrate with a semiconductor device manufacturing technique and sagging the moving ribbons relatively to the fixed ribbons. In such a diffraction grating, light amounts of regularly reflected light and diffracted light are changed by changing the depth of grooves. It is proposed that, in Japanese Patent Application Laid-Open No. 2004-4525, Japanese Patent Application Laid-Open No. 2002-72132, and Japanese Patent No. 3,522,133, a spatial light modulator in which light modulator elements are arranged in a line is applied to an image recording technique.
Meanwhile, since the moving ribbons are sagged in a state where their both end portions are supported, an amount of sagging of the both end portions becomes smaller than that of other portions of the moving ribbons. Therefore, if light is incident on the both end portions, light modulation by the light modulator element is failed to cause decrease in contrast or the like. To solve this problem, a linear illumination light with a very narrow width has to be accurately irradiated along the center of the line where the light modulator elements are arranged. Generation of such linear illumination light from a laser light requires expensive lenses with high quality which should be located in an optical system from a laser light source to light modulator elements, and this increases the manufacturing cost of an image recording apparatus.